Atmospheric carbon dioxide concentrations, 2004. The data reveal the seasonal changes in CO2. Red regions are producing CO2, blue regions are absorbing it. In the winter, much CO2 is released as plants are not photosynthesising as much, and organic matter decays. The pattern is reversed by the summer, where plants are photosynthesising much more, converting atmospheric CO2 into plant tissue. In the tropics, where the seasonal variations are not so pronounced, the deep red regions between July and October are largely due to human burning of foliage, for forest clearance or field preparation. The black and white dots show data collection points. Data from the NOAA Earth System Research Laboratory.